Material transport system

ABSTRACT

THIS INVENTION PROVIDES A POSITIVE DISPLACEMENT APPARATUS THAT ALLOWS ONE TO REPEAT AUTOMATICALLY IN A PRECISE MANNER THE ELUTING OR TRANSPORTING OF MATERIAL FROM A RESERVOIR, SUCH AS A COLUMN, TO A SECOND COLUMN OR A SECOND RESERVOIR. A MOTOR IS DRIVEN, UNDER CONTROLLED SPEED, TO DRIVE A PISTON INTO THE FIRST RESERVOIR AT A PRECISE RATE. AS THE PISTON ENTERS THE RESERVOIR, MATERIAL THEREIN, SUCH AS A LIQUID, IS FORCED UPWARDLY THROUGH AN APERTURE IN THE PISTON WHICH CO-ACTS WITH A TUBULAR ELEMENT CONNECTED TO THE SECOND RESERVOIR. PREFERABLY, THE BOTTOM OF THE PISTON IS CONCAVE AND THE PASSAGEWAY THROUGH THE PISTON HEAD BEGINS AT THE APEX OF THE CONCAVITY.

NOV. 16, 1971 R CONLON ETAL 3,62@,H

MATERIAL TRANSPORT SYSTEM Filed Sept. 30, 1968 2 Sheets-Sheet 1 Motor M0wr Speed $peed Conb'ol I @mdrol, 12

INVENTORS RaIplLDCcmIm, WilliamMlFLmIsIwr A TTORWEY NOV. 16, 1971 CONLQNETAL 3,62U,fl3$

MATERIAL TRANSPORT SYSTEM Filed Sept. 30, 1968 2 Sheets-Sheet 2 F .3, AA1 1 P f a /y v sob/m2 Solvent a g Composiliorz HTPOS IL 0 Solved 1 TimeorMillililers' Time OI'MillLlikm y. l r- '5. [v y 7 H Solveub SolveniSolvent Composition ZP/eJtt Sou/emf 1 Composition,

Sela/anti M Time orMillilifiers Time orMilliliiers mvmmns PhD-@0n10nWilliamMi'Yleishcr ATTORNEY United States Patent 3,620,134 MATERIALTRANSPORT SYSTEM Ralph D. Coulon, Wilmington, and William M. FleisherIV, Harmony Hills, Newark, Del., assignors to Nester & FaustManufacturing Corp., Newark, Del.

Filed Sept. 30, 1968, Ser. No. 763,632 Int. Cl. F15b 21/04; B67d /46;G011? 11/02 US. C]. 9279 3 Claims ABSTRACT OF THE DISCLOSURE Thisinvention provides a positive displacement apparatus that allows one torepeat automatically in a precise manner the eluting or transporting ofmaterial from a reservoir, such as a column, to a second column or asecond reservoir. A motor is driven, under controlled speed, to drive apiston into the first reservoir at a precise rate. As the piston entersthe reservoir, material therein, such as a liquid, is forced upwardlythrough an aperture in the piston which co-acts with a tubular elementconnected to the second reservoir. Preferably, the bottom of the pistonis concave and the passageway through the piston head begins at the apexof the concavity.

This invention relates to effecting separations and particularly toperforming separations by liquid chromatography. More particularly, itrelates to a transporting device that allows one to move fluid materialin a reservoir at a steady rate from the reservoir to a separator, suchas a packed column, or to a second reservoir or, if desired, the liquidor flowable mass may be transferred from successive containersultimately to a separating column or the like. The invention will beunderstood by reference to the following description and drawings, allof which are given for illustrative purposes only and are notlimitative.

In the drawings FIG. 1 is a front elevation, partly in section, showingtwo of the pumps of this invention;

FIG. 2 is a bottom plan view of the piston head taken on line 22 of FIG.1;

FIG. 3 is a block circuit diagram illustrating how the motors may bedriven to obtain a variety of flows and effects therefrom; and

FIGS. 4 to 7 show various flow patterns that can be effected by applyingthe principles and apparatus of this invention.

In performing separations by liquid chromatography, it is necessary totransport a liquid, such as a solvent, from a reservoir to a separationcolumn that contains materials to be separated. In the course of suchanalytical work it is frequently desired to mix two or more liquids toeffect elutions in a stepwise manner or with a smooth gradient.Hithertofore, ordinary pumping elements were used. With such it isnecessary to change the speed of one pump relative to the secondcontinuously to produce a gradient and to change the speed of the secondpump continuously to maintain a constant flow rate. Such manipulationsare complex and are very troublesome. These disadvantages are avoided bythe use of the apparatus of this invention which provides smooth,constant repeatable flow rates regardless of back pressure or changes inback pressure. This assures that the same analytical conditions will beobtained even if the columns are changed, repacked or compressed duringa run.

As can be seen in FIG. 1, a motor 10 is positioned to drive the screw11. The motor 10 is a digital motor which is driven at a constant speedwhich is set by and controlled by the motor and speed control 12. At theend of the drive 3,62%,134 Patented Nov. 16, 1971 screw 11 furthermostfrom the motor 10 is a captive nut 13 which is provided to facilitatethe removal of the pump ram 14 and the piston 15. In other words, shouldone desire to take out the piston assembly from the cylinder orreservoir 16, he merely twists the conventional captive nut 13 to thedesired release position. This disengages the pump ram 14 from the drivescrew 11 and allows the user to pull the pump ram and the piston head 15out of cylinder 16.

It is to be noted that the piston head contains seal rings 17. Theserings can be made of any of a wide variety of material that are inert tothe materials, such as organic solvents, that are being employed in thegiven analysis. Cylinder 16 is normally constructed of precise boreglass tubing and the piston element 15 is normally constructed ofpoly(tetrafluoroethylene). In high pressure work cylinder 16 isconstructed of an inert metal.

The motor, piston assembly and cylinder are held in cooperativerelationship by means of a frame work comprising the bearing support 18,main extension rods 19 and the bottom support 20. The cylinder 16 can bemounted in cylinder flange 21, and the cylinder can be readily detachedfor cleaning.

In the cylinder head or plunger 15 there is an internal boring 22 thepassageway of which co-acts with the passageway in the tubular element23 to form an outlet for the material contained in cylinder 16 as it isforced upwardly with the downward movement of the pump ram 14 shown bythe arrow in FIG. 1.

It is also to be noted that the bottommost surface of plunger 15 has acut-away section 25 which is concave. As the cylinder moves downwardly,any air trapped in the cylinder is forced toward the apex of theconcavity 25. Since the internal bore 22 has its inlet entrance at thevery apex of concavity 25, all of the air will pass through the bore 22and tubular element 23. In this way, entrapped air that would adverselyaffect the desired precise flow rates is avoided.

The concavity of plunger 15 is also shown in FIG. 2. There is also shownthe inlet entrance 26 to internal bore 22.

As can be seen from FIG. 1, a cylinder 16, such as the cylinder to theleft in FIG. 1, need not have any inlet in its bottom portion. However,if one wishes to use the pumps of this invention as a mixing device, thetubular element 23 of one cylinder 16 will be connected to an inlet 26at the bottom of the next cylinder 16. This is shown in the cylinder 16to the right in FIG. 1. Thus, the cylinder 16 to the left may containone material and the cylinder to the right may contain an entirelydifferent material. The operator can run the motors 10 for therespective cylinders at either the same or at different speeds andthereby effect the generation of linear and nonlinear gradients. Sincethe fiow rates of the different pumps are separately variable, theactual number of gradients and the flow rates at which the gradients canbe produced is quite large. Further, the user can select a givengradient and can repeat it preceisely as many times as he desires. Stillfurther, the user can terminate a given analysis or programming ormodify it at any time during the analysis by simply changing oroverriding the controls. Valves 28 may be placed in the lines atconvenient location to provide for opening and closing passageways.

The tubular elements 23 can be constructed of any of a wide variety ofmaterials. Generally, the tubing is a surgical grade narrow bore tubingmade of poly(tetrafluoroethylene) Through the positive displacementpumps of this invention a very substantial saving in time is effected inliquid chromatography. Precisely controlled and exactly repeatable flowrates are achieved regardless of column back pressure. Flow rates thatchange during a run are avoided. The researcher no longer has to put upwith columns that go dry or with plumbing failures or with collectionvolumes that are inconsistent. The researcher can very simply generateand repeat in exact manner any given solvent gradient. The motors areconstant speed, digital motors that have both a short and long termconstancy so that the flow rate is kept constant within :0.1%.

The term digital motor is used here to designate that class ofsynchronous motor which is driven with electronic circuits normallyassociated with digital computing elements, namely flip flop circuitsand one shot millivibrators. Rotation of the motor is by discreteincrements, normally 1.7 or per impulse received from the drivingelectronics. Motors and driving circiuts are available from SuperiorElectric of Bristol, Conn, trademark Slo- Syn. It is, of course, withinthe principles of this invention to use any of the many constant speedmotors well known in the art and that any constant speed motor can beused in the system of this invention alone or in con junction with anyother constant speed motor.

A block diagram (FIG. 3) showing how the digital motors can be driven atvarious speeds when taking the timing frequency from the normal 60 cycleper second power mains is presented. Using this scheme the maximum motorspeed is achieved when the motors are ad vanced at a rate of 60increments per second using the 60 cycle per second power mains as thepulse rate generator. Progressively slower speeds are obtained bydividing the 60 cycle per second pulse rate by standard electronicfrequency dividers such as flip-flop circuits which are described inelectronics text books. In this way 30 cycles per second, 15 cycles persecond, etc., are obliterated for slower pumping speeds.

In FIG. 3, a 60 cycle per second source 29 can be used as such directlyand sent to motors 30 and 31 through routes 32 and 33, respectively, ifdesired. The 60 c.p.s. source can also be fed to frequency dividers 34each of which successively divides the frequency in half. Thus, atjunction 35 a 30 c.p.s. source may be tapped through contact 36 which ispart of the speed selection system for motor 30. Similarly, junction 37may be used to use a 15 c.p.s. source for motor 30 by contacting element36 with contact 38. Motor 31 may be similarly handled through contact 39which is part of the speed selector limit for motor 31, there beingcontacts 40 for that motor. Thus, each motor may be given 60, 30, 15,7.5, 3.75 or 1.875 c.p.s. sources as desired with the set-up shown inFIG. 3.

Elements 41 and 42 are pulse shapers and elements 43 and 44 are pulseinverters provided for the respective motors 31 and 30.

Other sources of regulated pulse rate could of course be used, such as astandard variable frequency oscillator so that the motor speed and,therefore, pump rate could be continuously variable. For the presentapplication, however, the precision and repeatability of pulse rate ismore important than the variety of ratios so the 60 cycle per secondpower mains frequency was selected.

It is to be appreciated that in this and in all reservoirs theconventional magnetic stirring elements 45 and 46 may be used to effectstirring and that various kinds of flowable materials may be mixedand/or transported including pastes, powders, liquids and the like.Also, it is to be appreciated that the piston head 15 does not rotate asthe piston rides up and down, for the conduits 23 must remain fixed.Prevention or rotation is accomplished by means of pin 47, slot 48 andvertical plate 49 shown to the left in FIG. 1. Here a direct view isshown of plate 49 which has slot 48 in it in which slot pin 47 rides.The captive nut and piston ram are shown in dotted lines here, sincethose elements are behind plate 49 in this view. Pin or rod 47 isconnected at its far end to the captive nut 13 as shown in FIG. 1 to theright while at the end shown to the left, it is free to ride up and downin slot 48 the walls of which prevent rotation of the piston. The slot48 can, of course, have any length desired. For convenience, the plate49 is omitted in the unit shown at the right of FIG. 1.

Using the above described regulation of the motors 31 and 30, one canuse the same solvent in both or all the connected units in which eventFIG. 4 represents the straight line fiow. If the first pump containssolvent 1 and the second pump contains solvent 2 and the second pump isto follow the first, then the flow pattern that is obtained is thatgiven in FIG. 5. If different solvents are used and the second pump isnot to follow the first but the first is to discharge into the second,then the flow pattern will be a linear gradient such as shown in FIG. 6,if the two pumps are being run at the same speed. If the speeds aredifferent and the first pump is set at a rate slower than the secondpump, then the non-linear gradient given in FIG. 7 is obtained. Theslope given in FIG. 7 is reversed if the first pump runs faster than thesecond. It can be seen that a large variety of gradients can be producedand that any given gradient can be precisely repeated as long asnecessary.

While the invention has been disclosed herein in connection with certainembodiments and certain structural and procedural details, it is clearthat changes, modifications or equivalents can be used by those skilledin the art; accordingly, such changes within the principles of theinvention are intended to be included within the scope of the claimsbelow.

We claim:

1. A device for exerting pressure on a liquid contained in a vessel toeffect a positive, continuous displacement of said liquid out of saidvessel in a straight-line flow which device comprises a piston having aconcave bottom and containing an internal bore running from the bottomof said piston to its top, said bore having an aperture substantially atthe apex of said concavity whereby trapping of gaseous material, such asair, is prevented, said piston being adapted to be driven at a constantspeed in said vessel in a precise manner by a rotating drive element,said vessel having an orifice in conduit relationship with said bore andaffording said removal of said liquid from said vessel at a constantrate.

2. A device in accordance with claim 1 in combination with a tube inconduit relationship with the outlet of said internal bore at the top ofsaid piston.

3. A device in accordance with claim 2 in which said tube is also inconduit relationship with a second vessel.

References Cited UNITED STATES PATENTS 1,447,963 3/1923 Coleman 230221 X2,284,645 6/1942 Duffy 230-221 X 2,452,369 10/1948 Gravenhorst et a1.92-18l X 2,856,116 10/1958 Hogan 23022l X 2,953,119 9/1960 Geyer 92-18lX 2,966,145 12/1960 Froehlich 9218l X 3,331,328 7/1967 Smith et al.103-225 X WILLIAM L. FREEH, Primary Examiner US. Cl. X.R. 222-390

